Time courses of gst in response to elevated CO2 (A), reduced air humidity (B), darkness (C), and O3 pulse (D) together with corresponding changes in gst values (E–H) of the plants carrying mutations in the SLAC1 anion channel and protein kinases (OST1, CPK21, and CPK23) shown to activate SLAC1. Changes in gst (E–H) were calculated as shown in Figure 3, A to C. Significant differences (P < 0.05; n = 5–50) are denoted with different lowercase letters.